1. Field of the Invention
The present invention relates to an apparatus and a method for acquiring synchronization to support multi-Frequency Allocation (multi-FA) in a mobile communication terminal. More particularly, the present invention relates to an apparatus and a method for acquiring synchronization by sharing a Voltage Controlled Temperature Compensated Crystal Oscillator (VCTCXO) control signal generator and a baseband digital Phase Locked Loop (PLL) between FAs in a mobile communication terminal which supports the multi-FA.
2. Description of the Related Art
As WiMAX technology is advancing and being applied to mobile access systems, various operation scenarios are being suggested to replace the existing communication service standards. For instance, according to an operation scenario under consideration, one terminal provides multiple services at the same time by supporting a multi-Frequency Allocation (multi-FA). That is, the terminal provides both voice call and data service through one FA and provides a specialized service, such as a broadcasting service, through a separate FA.
To support the multiple services at the same time, a conventional terminal supports the respective FAs by using separate components and paths for each of the FAs of the corresponding services respectively. For example, the terminal of FIG. 1 includes two modems 101 and 111 that are separated from each other to support two services at the same time. When the terminal includes the two separate modems as shown in FIG. 1, the volume of the hardware is increased. Since the modems individually maintain the synchronization, when switching is performed between two FAs or a state mode (e.g., normal mode, sleep mode, and idle mode) is changed, it takes a considerable time to acquire the synchronization. As a more detailed example, when modem 101 of the two modems 101 and 111 normally operates by acquiring the synchronization for a specific FA, and a service using another FA is added in conformity with the mobile WiMAX standard, the other modem 111 operates separately from the specific FA and initiates frequency and time offset estimation to acquire the synchronization of the other FA.
FIG. 2 is a flowchart illustrating a conventional method of a mobile communication terminal for acquiring synchronization for two FAs.
In step 201, the terminal determines whether a service using a first FA commences. When the service using the first FA commences, the terminal acquires synchronization by estimating frequency and time offset values for the first FA in step 203 and enters a normal state with respect to the first FA in step 205. Then, the terminal proceeds to step 207. When the service using the first FA does not commence in step 201, the terminal goes to step 207 without intervening steps 203 and 205.
In step 207, the terminal determines whether a service using a second FA commences or not. When the service using the second FA commences, the terminal acquires synchronization by estimating frequency and time offset values of the second FA in step 209. In step 211, the terminal enters a normal state with respect to the second FA and then finishes this process. When the service using the second FA does not commence in step 207, the terminal finishes this process.
As discussed above, the conventional terminal uses two independent modems to support two FAs and the two modems independently acquire the synchronization for their own FA. As a result, the volume of the modem is increased which causes an inconvenience to the user by making the terminal itself larger. Also, it takes a considerable time for the modem to acquire the synchronization of the FA and thus delays the service start time.